1. Field of the Invention
The present invention relates generally to apparatus for mixing additives and water for medical purposes, and more particularly, but not by way of limitation, to apparatus for mixing a bicarbonate solution for use with dialysis machines.
2. Description of the Prior Art
Conventional prior art centralized mixing systems have used a mixing tank into which water was directed and into which bulk quantities of powered additives have been dumped into the open top of the tank. The water and dry additives are then mixed through the use of a mechanical mixer. The mixed solution is then pumped to a storage tank from which it is delivered to the individual dialysis machines.
There are several problems with such systems. First, the mixing tank is typically an open top tank which allows the mixture to be contaminated which leads to medical complications for the patients using the mixture. Second, it is physically difficult to lift the large bags of bulk material into the open top tank, and the operation of this equipment leads to many on-the-job injuries, such as back strains and the like.
Centralized bicarbonate systems are frequently cited as the source of water born bacteria and endotoxin. This probably results from the enhancement in the growing medium (permeate solution typically has too little nutrient to support bacteria growth) and the fact that the system is open for charging and mixing for extended periods of time.
One other system which has been more recently developed to provide preparation of fluid concentrates is that shown in U.S. Pat. No. 5,344,231 to Jonsson, et al. The Jonsson, et al. system utilizes a cartridge apparatus for the mixing of concentrate and water at the immediate location of the dialysis machine. The primary difficulty with the Jonsson, et al. system is its high cost.
Thus, it is seen that there is a need in the art for improved systems for mixing of water and additives for medical uses, and particularly to provide bicarbonate solution to dialysis machines, while eliminating the problems of the various prior art systems discussed above.
The present invention provides a system for mixing water and an additive to form a concentrate solution. The system includes a mix tank having an outlet. A pump has a suction inlet connected to the outlet of the mix tank, and has a pump discharge. An eductor has a fluid inlet and a fluid outlet with a flow path connecting the fluid inlet and the fluid outlet. The eductor has an eductor inlet connected to the flow path. The fluid inlet of the eductor is connected to the pump discharge. An additive container has an outlet connected to the eductor inlet, so that additive stored in the additive container is drawn therefrom by the flow of fluid through the flow path of the eductor. A return line connects the fluid outlet of the eductor to the mix tank. Thus, a closed system is provided in which water and the dry additives may be mixed by a combination of the mixing activity which takes place in the eductor and the piping downstream of the eductor and by further mixing action which takes place as the mixture is re-circulated back through the mix tank.
The present invention is developed to reduce the opportunity for having an open tank while preparing dialysate and to make the mixing process more ergonomic and faster. This is accomplished by reducing the height of the port for charging the solid bicarbonate powder, using a funnel and ejector to wet and mix the powder with circulating permeate and agitating the mix tank with nozzles driven by the re-circulating flow of fluid.
It is therefore a general object of the present invention to provide an improved system for mixing water and additives to form concentrate solutions for medical uses.
Still another object of the present invention is the provision of an additive mixing system which is completely closed so as to prevent contamination of the solution.
Yet another object of the present invention is to provide a system for mixing water and additives which does not require bags of additive powder to be lifted overhead into large mixing tanks.
Still another object of the present invention is the provision of systems for mixing water and additives which are economical.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon reading of the following disclosure when taken in conjunction with the accompanying drawings.